Production of gelatin printing reliefs



Patented Oct. 31, 1939 Walter Frankenburger, Habana, Cuba, and Georg Rjissier, ppau, Germany, assignors, by mesne assignments, to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of Delaware No Drawing.

The present invention relates to the production of gelatin printing reliefs.

Positive gelatin reliefs suitable for producing color pictures by ir'nbibition processes or other means from negatives to be printed in the usual photographic way made by exposing a silver halide gelatin emulsion layerunder the negative through the layer support, then developing with a tanning developer and finally dissolving aratingit by means of an enzyme that degrades gelatin, for instance pepsin or papain. This operation produces from a negative a positive relief which may be used for printing. It is'one object of this invention to provide a process which yields by the known method of etching with hydrogen peroxide 9. positive relief from a negative to be printed, amethod by which in itself a positive relief is obtained from a positive to be printed or a negative relief from a negative to be printed.

Further objects of the invention will appear from the detailed description following hereinafter.

The nature of the invention may be described as follows:

The ,silver halide layer is exposed behind the negative to be printed either in contact or by projection. Development followsin a developer which hardens the gelatin proportionally to the developed silver or permits the silver to remain in a form which makes it unsuitable for catalyzing the liquefaction effect on the gelatin of the hydrogen peroxide etching process. Altematively, one may develop with an ordinary developer, for instance a glycin developer or a l -hydroxy 4 -methylaininobenzenesulfate hydroquinone developer, and subsequently by means of a known hardening bath containing, for instance copper sulfate and bichromate, harden the gelatin proportionally to the silver and thus make it resistant to etching. The residual undeveloped silver halide is now reduced to silver. This may be done by exposure to diffused light and developing with a developer which does not affect and the removal of the unhardened gelatin occurs only at the silver of the second developed image, so that as a result there remains a positive relief corresponding with the first developed 5 image.

the non-hardened gelatin with hot water or septhe gelatin or by reduction with a strong reduc- Application January 11, 1939, Serial N0." 250,358.

5 Claims. (ores-as) "G rma y anuary 12,

The process is not limited to the use of ordinary black and white negatives but with obvious modification is applicable for producing correct color copies or enlargements from color negatives, for instance the complementary color neg- 5 atives of the three-layer color development process.

t The following example illustrates the invenion:

A film carrying an emulsion comparatively poor 10 in silver is exposed behind a Lei'ca negative by projection and developed at 18 C. with a developer of the following composition:

. Cubic centimeters Potassium carbonate solution-oi 20 per 15 cent. strength 10 Pyrocatechol solution of 2 per cent strength 10 Water 00 "After 5 minutes the development is interrupted in an acid .bisulfite solution, the film is washed for about '5 minutes and then blackened in bright light for 5 minutes in a normal glycindeveloper. The now uniformly black film is washed for 10 .minutes and treated at 22C. for 2 minutes in a the following etching bath:

. .Cubic centimeters Copper sulfate solution of 7.5 per cent strength -L 30 Potassium bromide solution of 0.2 per cent 30 strength 30 Sulfuric acid of 2.5 per cent strength 30 Hydrogen peroxide of 3 per cent strength 45 After a short sojourn in an acid fixing bath which positive gelatin relief with pure whites. This relief may be dyed with acid dyestuffs and printed on a gelatin paper by the'usual imbibition process.

It is obvious that the process is applicable to 40 producing negative gelatin reliefs from diaposi tives.

We claim:

1. In a process for the production of a gelatin relief by the hydrogen peroxide etching method, the improvement which comprises exposing a. silver halide gelatin emulsion layer through the 1 support of said layer, producing the latent image by development, hardening the gelatin proportionally to the developed silver, exposing the layer 60 to diffused light, treatingthe layer with a developer incapable of affecting the gelatin, and transforming the layer to a relief;

2. In a process for the production of a gelatin relief from a. negative by the hydrogen peroxide etching method, the improvement which comprises exposing a silver halide gelatin emulsion layer under said negative through the support of said layer, producing the latent image by development, hardening the gelatin proportionally to the developed silver, exposing the layer to diffused light, treating the layer with a developer incapable of affecting the gelatin, and transforming the layer to a relief.

3. In a process for the production of a gelatin relief from a positive by the hydrogen peroxide etching method, the improvement which comprises exposinga silver halide gelatin emulsion layer under said positive through the support of said layer, producing the latent image by development, hardening-the gelatin proportionally to the developed silver, exposing the layer to diffused light, treating the layer with a developer incapable of afiecting the gelatin, and transforming the layer to a relief.

4. In a process for the production of a gelatin relief by the hydrogen peroxide etching method,

the improvement which comprises exposing a silver halide gelatin emulsion layer through the support of said layer, producing the latent image by development, the developer being capable of hardening the gelatin proportionally to the tieveloped silver, exposing the layer to difl'used light, treating the layer with a developer incapable of affecting the gelatin, and transforming the layer to a relief.

5. In a process for the production of a gelatin relief by the hydrogen peroxide etching method, the improvement which comprises exposing a silver halide gelatin emulsion layer through the support or said layer, producing the latent image by development, the developer being capable of converting the silver into a compound resistant to etching with hydrogen peroxide, exposing the layer to diffused light, treating the layer with a developer incapable of affecting the gelatin, and transforming the layer to a relief.

WALTER GEORG ROSSLER. 

